Several methods are currently available to form a channel through a blocked blood vessel. Initially, a guidewire is used to probe a channel through the blockage in the blood vessel in order to reach a downstream unblocked blood vessel portion. After the guidewire has been advanced through the blockage, an angioplasty balloon catheter is passed over the guidewire and is inflated to dilate the blockage.
This method is known to succeed in soft or partial blockages of a blood vessel, through which the guidewire can be easily passed. It carries the risk, however, of causing tears in the arterial wall due to the diameter of the inflated balloon. Moreover, such methods do not remove the atheromatous material from the vessel.
Other methods use catheter devices having a rotating or vibrating tip operated by an external drive unit or power source, which is coupled to the tip by a flexible drive element, such as a cable, spring or shaft. Such devices such as disclosed in U.S. Pat. No. 6,818,002 are introduced into a blood vessel over a guidewire, and the atheroma or blood clot material is shaved from the wall of the artery and may then be aspirated by the catheter out of the vessel in order to prevent distal embolization.
These methods are known to be insufficient to remove all the atheroma or blood clot material from the blood vessel because of the limited size of the rotating tip. For example, the diameter of the rotating tip cannot generally be much larger than the diameter of the catheter, which is usually limited to 1.5-2.5 millimeters. Such devices can form a channel only of this diameter, regardless of the vessel diameter and the atheroma or blood clot material volume.
Some rotating catheters having expandable tips in form of baskets or loops that adapt to the vessel size are known in the prior art, for example US 2002/0010487, U.S. Pat. No. 7,108,704 and US 2013/0103046. The manufacturing costs and the complexity of such catheters are high and their shaft diameter is usually relatively large. Moreover, the design of such devices usually provides poor aspiration capabilities, poor flexibility which limits maneuverability within curved blood vessels, and the inability to open a total occlusion in a blood vessel whose hardness prevents the guidewire from passing therethrough.
Such prior art devices are introduced into the blood vessel through an introducer sheath of a guiding catheter, necessitating that the effective cross section of the shaft used for aspiration will be smaller than the cross section of the introducer sheath or of the guiding catheter.
Expandable devices are also disclosed in U.S. Pat. No. 5,030,201 and U.S. Pat. No. 6,146,396.
U.S. Pat. No. 7,316,697 discloses a vessel cleaning system for removing an obstruction from within a patient's vessel. A flexible distal-agitator is connected to the agitator-shaft and shaped so that it is asymmetrically offset to only one side of the longitudinal axis of the agitator-shaft. The agitator-shaft is extended from an open distal end of the flexible-tube to break the obstruction into pieces while rotating with an effective diameter that is larger than its cross-sectional diameter. The agitator-shaft has difficulty in being introduced to both large and small sized blood vessels. This device cannot be advanced over a guidewire and cannot open a total occlusion.
It is an object of the present invention to provide an atherectomy device that can be selectively introduced to both large and small sized blood vessels.
It is an additional object of the present invention to provide an atherectomy device that can open a total occlusion and to then permit passage of a guidewire downstream to the opened occlusion site, for additional atheroma removal.
Other objects and advantages of the invention will become apparent as the description proceeds.